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Lying On Certain Days of the Week

Angel lies on Mondays, Tuesdays and Wednesdays but tells the truth the rest of the week.

Brenda lies on Thursdays, Fridays and Saturdays, but tells the truth every other day.

Angel says, “Yesterday I was lying.”

Brenda replies, “So was I.”

What day was it?

Thursday.

Putting the information in a table makes it easier to solve. We’ll use A for Angie, B for Brenda, T for truth and F (false) for lying.

  S M T W Th F S
A T F F F T T T
B T T T T F F F

To begin with, there aren’t any days where both of them told the truth and lied the day before, so we know one of them must be lying.

So we have two options, either Angel is lying or Brenda is.

Option 1. Angel is lying.

In order for this to be the case, she needs to be lying today and telling the truth yesterday, so we need two days in a row with T F. And if Brenda is telling the truth, she would need two days with F T. That means we’re looking for two days that have

Angie:  T F
Brenda: F T

Option 2. Brenda is lying.

This is just the reverse of the above, so we need to find:

Angie:  F T
Brenda: T F

The only day that matches either of the two options is Thursday, and it’s option 2. Brenda is the liar.


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6 Comments on "Lying On Certain Days of the Week"


Tobey Auspland says
November 6, 2015 @ 10:38

It’s Sunday.


Prince Icons says
November 15, 2015 @ 16:07

Sunday


Natalia says
November 22, 2016 @ 16:08

Not Sunday. Both of them tell the truth on Sunday. Yet I don’t get how this is Thursday. Can anyone explain?


Rian says
November 27, 2016 @ 15:31

It is thursday because angle stops lying on that day. So angel tells the truth that she was lying on Wednesday. Then Brenda started lying on Thursday and lies saying she lied on Wednesday. So therfore it is thursday


Zack. B. Claasified says
January 19, 2017 @ 20:25

Oops.
I thought it was Sunday…
Man, I’m starting to get an inferiority complex from not being able to grasp the answers on some of these…


Gabriel says
May 26, 2017 @ 09:33

Thursday of course


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